Heat exchanger package for high-density, high-powered electronic modules



Nov. 12, 1968 J. M. BLOCK 3,411,041

HEAT EXCHANGER PACKAGE FOR HIGH'DENSITY, HIGH-POWERED ELECTRONIC MODULES 6 Sheets-Sheet 1 Filed July 17, 1967 Fig. 1.

Jay M. Block,

INVENTOR.

Nov. 12, 1968 J. M. BLOCK 3,411,041

HEAT EXCHANGER PACKAGE FOR HIGH-DENSITY, HIGH-POWERED ELECTRONIC MODULES Filed July 17, 1967 6 Sheets-Sheet 2 d 6 0 0 N o In 8 E l \JN N O J N a o .9 1 d LL 8 ecooooc o f ri m I lllukaouockol h: I" 8 Jay M. Block,

INVENTOR.

Nov. 12, 1968 J. M. BLOCK 3,411,041

HEAT EXCHANGER PACKAGE FOR HIGH-DENSITY, HIGH-POWERED ELECTRONIC MODULES Filed July 17, 1967 6 Sheets-Sheet 5 Fig. 3.

Jay M. Block,

INVENTOR.

Nov. 12, 1968 J. M. BLOCK HEAT EXCHANGER PACKAGE FOR HIGH-DENSITY, HIGH-POWERED ELECTRONIC MODULES 6 Sheets-Sheet 4 Filed July 17. 1967 3,411,041 -POWEREID Nov. 12, 1968 J. M. BLOCK HEAT EXCHANGER PACKAGE FOR HIGH-DENSITY, HIGH ELECTRONIC MODULES 6 Sheets-Sheet 5 Filed July 17, 1967 I em eee e wo 7a omweoo pmwe 3,411,041 POWERED Nov. 12, 1968 J. M. BLOCK HEAT EXCHANGER PACKAGE FOR HIGH-DENSITY, HIGH ELECTRONIC MODULES 6 Sheets-Sheet 6 Filed July 17. 1967 Zita a ggggggg ooooooooooo%ooooooo\oooo United States Patent 3,411,041 HEAT EXCHANGER PACKAGE FOR HIGH-DEN- SITY, HIGH-POWERED ELECTRONIC MODULES Jay M. Block, Thousand Oaks, Calit., assiguor to Hughes Aircraft Company, Culver City, Calif., a corporation of Delaware Continuation-impart of application Ser. No. 603,833, Dec. 22, 1966. This application July 17, 1967, Ser. No. 668,727

12 Claims. (Cl. 317-100) ABSTRACT OF THE DISCLOSURE A package for dissipating large quantities of heat per unit volume from a high-power, high-density electronic system assembled from a base plate and at least two electronic modules. Each module includes electronic components and circuitry and a rigid frame supported on and by the base plate and all the modules are structurally united together by tension bolts passing through the frames. Each frame includes a plurality of large area parallel webs to form compartments or cells for a series of printed circuit cell cards. Passages for flow of a coolant are formed in the frames adjacent the webs. When the modules are assembled, the passages, which are electrically insulated from, but in thermal contact with the cells and the cell cards, are aligned to provide continuous conduits permitting the flow of the coolant.

The present invention is a continuation-in-part of copending application Ser. No. 603,833, filed Dec. 22, 1966, noW abandoned, entitled, Package of Electronic Modules.

The present invention relates to a heat exchanger package for complex, high-density and high-powered electronic systems and, more particularly, to such a package comprising a number of modules each of which supports electronic components and which, when assembled rigidly together, includes an integral heat dissipating system. As used herein, the term module designates a frame structure or member and an assembly of electronic components which are built in a standardized size, which have standardized plug-in or solderable terminals, and which is supported by the structure. The module is typically used in combination with other modules or assemblies to form a complete electronic system.

Complex electronic systems having many thousands or tens of thousands of components are large and bulky in size and are conventionally packaged in an assembly through the use of such structural members as angles, brackets, cold plates, heat sinks and other pieces of hardware. Such pieces of hardware are used to structurally integrate the various components of the system and generally form no part of the system itself; their existence by nature adds weight and bulkiness to the resulting assembly. In addition, such systems are relatively easy to cool since the components are sufiiciently separated so that the power rating per cublic foot and the resulting generated heat is sufi'iciently low to permit the use of conventional heat exchanging means. Thus, it is usual first to design an electronic system and then to adapt some form of heat exchanging means thereto.

With the increasing need for lightweight systems, prior electronic systems have undergone a change in design, particularly in the use of miniaturized and compact circuits, thus greatly increasing the power rating per cubic foot over prior systems and necessitating a re-evaluation of cooling means to effectively dissipate the larger quantities of heat per unit volume generated by densely packaged electronic components. It has been estimated that ice conventional heat exchanging means is adequate to dissipate the heat produced by a system producing 0-300 watts per cubic foot. From 300-600 watts/-ft. a small air flow, perhaps laminar air, is required. Between 600- 1200 watts/ft. a forced air flow or the equivalent is required. Above 1200 watts/ft. the heat dissipation problems becomes so aggravated that totally new concepts of thermal management must be formulated. With the present invention, it has been found necessary first to design the heat-exchanging means with a large heat dissipating area, and then to build the electronic components and circuitry around the basic heat exchanger, a concept which is contrary to the usual design of electronic systems.

The present invention, therefore, relates to a package design for a complex electronic system including an integral large area means for dissipating the heat generated by the numerous electronic components of the system and for structurally integrating a number of modules contain ing the electronic components into an assembly without the use of auxiliary structural elements or hardware. The components are integrated on cell cards and the heat dissipating means is so designed that separate heat dissipating members, such as heat sinks and cold walls, are not required.

Briefly, the improved package of the present invention includes a base plate which contains a plurality of electrical connectors and supports at least two electronic modules. Each module comprises a rigid cold frame member and electronic components and circuitry which are supported thereby. The rigid cold frame member includes large area heat conducting webs to provide structure for the modules. The plurality of electronic components are arranged in such a manner on insulated cell boards as to provide a large area and the boards are placed in contact with the large area webs so that the heat generated by the components is easily conducted to the webs and thence to the frame. The frame members are mounted on the base plate and support the components which are in electrical contact with the base plate connectors. The frame members also contain a plurality of heat exchange passages and are rigidly integrated into a single unit or assembly by a plurality of tension bolts extending through the assembled frames to align the passages in adjacent frame members into a plurality of continuous conduits, thus providing a continuous flow path for a cooling medium which dissipates the heat conducted through the webs and to the frame.

To provide the large arrangement of electronic components, a plurality of spaced circuit or cell cards are utilized. Each cell card includes several components which are contained on one side of a cell card board and all of the cell cards are electrically and mechanically mounted on motherboards at right angles thereto. The motherboards have contacts which electrically connect with the base plate electrical connectors.

The heat conducting Webs of the cold frame members are parallely secured within the frame members to provide a series of cells. The cell cards are placed within the cells and are closely spaced from each other. The sides of the boards opposite from the components are placed in contact with the webs. Both the cell cards and the webs have large surface areas so that even if a small amount of air or other insulator exists between the card boards and the webs, heat from the cards and the components thereon is easily transferred by virtue of the large surfaces to the webs and thence to the frame members and to the coolant flowing through the passages therein.

To optimize heat transfer from the frame members, the passages are adapted to have several configurations which are suited specifically to the flow rate and the type of cooling medium.

It is, therefore, an object of the present invention to provide an integral heat exchanger and package for an electronic system.

Another object is the provision of a heat exchanger package having a large heat dissipating surface area.

Another object is to provide a structure for a high density of electronic components per unit volume.

Another object is the provision of an electronic pack age which can be easily assembled and disassembled.

Other aims and objects, as well as a more complete understanding of the present invention, will appear from the following explanation of exemplary embodiments and the accompanying drawings thereof, in which:

FIG. 1 is a perspective view of one embodiment of an assembly of electronic modules constructed in accordance with the principles of the present invention;

FIG. 2 is an exploded view of the assembly illustrated in FIG. 1 showing the various frame members, modules and elements comprising the assembly;

FIG. 3 is a partial sectional view, taken along line 33 of FIG. 1, illustrating the passages aligned in the frame members to provide continuous conduits for a cooling medium, with one wall of plate 28 removed;

FIG. 4 is a perspective view of one of the frame members and webs of FIG. 1;

FIG. 5 is a perspective view in partial section of the back side of another of the frame members and Webs of FIG. 1 with a cutaway portion of the back side of a motherboard;

FIG. 6 is a perspective view in partial section of the front side of the frame member illustrated in FIG. 5 with a few cell cards having electronic components thereon and with a cutaway portion of one flexible stabilization element secured thereto;

FIG. 7 is an elevational view of the back side of a I third frame member of FIG. 1 and illustrating a heat exchange method;

FIGS. 8(a)(d) are elevational views in section of various coolant flow paths in the frame member;

FIG. 9 is perspective view in partial section of a motherboard and four illustrative circuit or cell cards and electrical connections thereof;

FIG. 10 is a side view of a portion of a flexible element used to stabilize the cell cards in the frame members; and

FIG. 11 is a partial view in section of the arrangement of cell cards and webs taken along line 11-11 of FIG. 6.

Accordingly, with reference to FIGS. 1-3 a plurality of individual electronic modules 10, 12, 14 and 16 comprising electronic components and structured heat exchanging means is supported by and attached to a mounting plate or base plate 18 by a plurality of short bolts or jack screws 21 (see FIGS. 2 and 3). The modules and frames further are rigidly united and packaged into an integrated assembly 19 by a plurality of tension bolts 20 which extend transversely of the assembly through bores 20a in the modules. The package shown in FIG. 1 typically has a size in the order of an eightinch cube and includes adjustable fasteners 22- for attaching the unit to a preliminary structure such as an equipment rack which contains many electrically interconnected systems. In addition, a plurality of shear pins 24 are provided on one end 25 of base plate 18 so that the contact elements of an interconnecting electrical connector 26, mounted on the end 25, may be secured to a mating connector (not shown) on a primary structure.

As illustrated in FIG. 3, an end plate 27 is secured to the frame of module 10 by bolts 20 and a plurality of short bolts 23. A Walled plate 28 is aflixed by conventional means, such as welding, to end plate 27 of the package to define a chamber 29 with the surface of plate 27. A cylindrical nozzle or port 30 extends from plate 28 and opens into chamber 29 so that a source of cooling medium, such as air, may be introduced into the chamber. It is to be understood that other openings in walled plate 28, plate 27, or module 10 may be used for supply of the coolant.

As shown in FIG. 2, base plate 1 8 includes a plurality of electrical connectors 32 which are afiixed in a predetermined arrangement on one surface 34 of the base plate. Each of connectors 32 is positioned for engagement with a mateable connector on each of the ends of electronic modules 10, 12, 14 and 16. The electronic components associated with each module as well as the mateable connectors are briefly described below and their connections are more fully disclosed in copending patent application Ser. No. 561,978 filed Sept. 29, 1965, entitled, Circuit Board With Integral Contact Elements, by Donald S. Kelly, Richard D. Obert and Richard F. Stewart and assigned to the same assignee of this application, although it is to be understood that other rightangled configurations are as applicable. Each of connectors 32 has its contact elements electrically connected to one or more of the contacts on interconnecting electrical connector 26 through electrical conductors which are located on the underside of base plate 118. Thus, electrical paths are maintained fro-m each of the contacts of interconnecting connector 26 to the electronic components and circuits on the modules through connectors 32 on base plate 18 and the modules.

To support the electronic components and circuits, each of modules 10, 12, 14 and 16 includes a rigid frame member 36. Each frame member is configured in the preferred embodiment to support the components and circuits as set forth below for integration into the package or assembly as shown in FIG. 1. While four modules have been shown in a specific relationship in the FIGURES, it should be understood that this relationship and the number of modules has been shown only for illustrative purposes since a greater or lesser number of modules and their specific arrangements may be made without departing from the scope of the present invention. In addition, although each module has been configured differently from the other modules, it is to be further understood that the specific configurations are set forth only as illustrative of the present invention.

Each module is structurally supported by its frame member 36 into which through passages 38 are formed, for example, by boring or milling. Webs 39, see FIGS. 2 and 4-8, are integrally formed in the frame members and are parallely disposed with each other to form cells 44 in frame members 36. The webs are thin with a relatively larger depth than their thickness to provide large upper and lower surfaces for dissipation of heat and, as disclosed below, each of cells 44 provides an opening for the placement of two cell cards so that the heat generated thereby will be easily transferred to the large surface area webs.

When the modules are secured together into integrated assembly 19 and the assembly is placed into use, any heat generated by the electronic components on the cell cards is conducted away by the webs toward the frame members and to passages 38. The coolant flowing through passages 38 thereupon picks up and exhausts the heat from the assembly.

To provide through passages in assembly 19 (see FIG. 3 in particular), plate 27 is provided with a plurality of perforated slots 31 which open into chamber 29. The slots and passages are so located that, when frame members 36 are assembled into the package, the passages in adjacent members are aligned with the slots to define continuous passages from chamber 29 to the opposite end of the package. In the illustrated preferred embodiment, it has been found desirable to exhaust the cooling medium from the side of the package (see FIGS. 1 and 2) rather from the end as would be the case if the continuous passages extended from end to end; To achieve this desired result, a plurality of horizontal slots 40 (FIG. 2) are provided in the inside surface of electronic module 16. Each slot 40 is aligned with one or more of passages 38 of module 14 and extends to at least one side of the passage where it opens into a recess 41 (FIG. 1) in module 16.

In order to prevent flow of coolant from horizontal slots of module 16 from contaminating the electronic components, insulating plates 47 are secured to the back side of module 14, as depicted in FIG. 7, in order to close off one side of the horizontal slots and to form horizontal conduits leading to recess 41.

Thus, the coolant is passed through the assembly by introducing it into chamber 29 through port 30 and conducting it along each of passages 38 without contacting directly any of the electronic components or circuits. Since frame members 36 and webs 39 are constructed of a rigid material having a high thermal conductivity, such as afforded by an aluminum alloy, the continuous flowing of the cooling medium through the passages results in a conduction of heat away from the package by the coolant.

In the preferred embodiment of the present invention, the cooling medium is described as being introduced into chamber 29 and distributed throughout by perforated slots 31 in front plate 27 and passages 38. It should be understood that, if desired, plate 28 and resulting chamber 29 may be eliminated and that the cooling medium may be introduced into passages 38 directly through apertures in front plate 27.

As shown in FIGS. 3 and 4, a number of slots 42 are provided in the frame member of module 10. The slots function similarly to passages 38 in order to conduct the cooling medium and reduce the possibility of misalignment between the passages of adjacent frame members. While passages 38 have been illustrated as extending transverse of the frame members, if desired for increased cooling, additional passages can be provided in the frame member and such passages can extend in any desired orientation.

One such additional passage is depicted in FIGS. 3 and 4 and comprises a longitudinally extending slot 46 in which a plurality of fins 48 are provided. Coolant from slot 42 flows through slot 46 and is exhausted through an opening 50 at the other end of slot 46. Slot 46 and fins 48 are useful when particularly high-powered components, which produce a corresponding large amount of heat, must be afforded a larger cooling area. When the components used are of relatively low power and produce a correspondingly small amount of heat, they may be mounted on a circuit board, such as suggested by the dashed enclosure of numeral 52 of FIG. 4, and may be secured to frame 36 of module by screws 53.

When the coolant comprises very clean air or other medium having a good dielectric constant, it is possible to utilize the flow paths depicted in FIG. 7. Here. slots 42 are formed in frame member 36 and cuts 54 are made in the frame member between the slots and cells 44. One or more separators 55 may be provided in slots 42 so that coolant may flow parallely and/or in series through cells 44 and over the electronic components.

A series of scallops 57 (see FIG. 4) may also be formed in webs 39 to aid thermal conduction and, if desired, the scallops may be shaped to conform to the shape of resistors, capacitors and other insulated components to increase the heat conductive surfaces.

In addition to the configuration of passages 38 as holes or as slots 42, the passages may be configured accordi g to thermal requirements as illustrated in FIG. 8. In FIG. 8(a) passages 38 take the form of holes 90. In FIG. 8(b) the passages are configured as elongated slots 92. The passage of FIG. 8(a) is a long slot 94. In FIG. 8(d) corrugations 96 of aluminum. for example, are placed within slot 94 of FIG. 8(a). Although these passages are differently configured, they are illustrated as representative of a multitude of different forms which may be used for exhausting the coolant which flows through the passages. The selection of a passage configuration is dictated generally by the system requirements. In general, the factors of pressure drop and quantity of fluid per unit time, i.e., flow rate, are important, Depending upon whether the pressure drop or the flow rate is most important, the configuration of the passages will differ. For gasses, an oval slot such as that depicted in FIG. 8(b) is preferred where the coolant is under a high pressure but at a low flow rate. A milled slot is useful when both the pressure and the flow rate are moderate. The corrugated thin stock passage of FIG. 8(d) is employed when the pressure is low and the fiow rate is high. Very small holes, as depicted in FIG. 8(a) are used when the coolant comprises a liquid.

Where it is necessary to provide a maximum heat dissipation for components, a circuit board 56 as depicted in FIG. 9, having connections which are more fully disclosed in copending application Ser. No. 561,978, may be utilized. Circuit board 56 comprises a series of base members or cell cards 58 and a motherboard 60. A plurality of miniaturized components 62 and conductors 64 are located on boards 65 of cards 58 and are secured to the motherboard through holes 66 and other connections. The components on two adjacent boards 65 face each other and the other side of each board is free from components so that the other sides may be placed in contact with webs 39. Electrical leads 68 extend along motherboard 60 and are secured to one or more contact elements 70 which are contained in a channel or header 72. A plurality of holes 74 are provided in the header and in the motherboard (see also FIG. 5) so that circuit board 56 may be affixed to frame member 36 by screws or other means. The distance between the component free side of one of cell cards 58 and the component free side of another cell card is adjusted to conform with the thickness of webs 39 and to permit their insertion within cells 44 so that each web is embraced by the adjacent component free sides of adjacent cell cards.

The arrangement of cell cards and webs differs substantially from conventional mountings of well-known circuit boards. Such well-known circuit boards are usually stacked on top of each other and are interconnected by means of multiple layers of interconnecting means to result in a large area-low volume assembly. Such a layered and stacked arrangement, however, requires a volume which is greater than that of the stacked circuit boards to enable the proper connections to be made. Thus, some volume in the stacked arrangement is wasted and such an arrangement may be viewed as essentially a two-dimensional arrangement.

The present invention more efficiently utilizes the available space and may be viewed as a three-dimensional arrangement. As described above and hereinafter, circuit boards 56 have cell cards 58 disposed at right angles to motherboard 60. This arrangement permits a higher density of electronic components to be placed within a given volume than in prior stacked arrangements. Because of this increased density, a higher power per unit volume is obtainable. However, by use of the present invention, the heat produced by the three-dimensional arrangement is dissipated by the very large conducting surface provided by webs 39 by means of thermal contact with one side of each cell card 58.

As shown in FIG. 5, one edge of each of the webs is recessed and is provided with steps 76 so that the back of the motherboards will fit flush with one face of the frame member and so that the front of the motherboard will be spaced from the webs to preclude possible electrical contact therewith. A plurality of board connections 78 are formed on one recessed surface of each frame member 36 so that circuit boards 56 may be secured thereto.

A series of indentations 80 (see FIG. 6)are formed on the other side of the frame members so that a tracklike member 82 (see also FIGS. 10 and 11) may be affixed to members 36 through holes 84 by connectors 83. Members 82 are provided with a plurality of protuberances 86 which are designed to fit within cells 44 and between adjacent cell cards 58 at their component faces in order to securely hold the component free sides of the cards within cells 44 and against webs 39 and to prevent electrical contact between the components on the adjacent cell cards.

Although the invention has been described with reference to a particular embodiment thereof, it should be realized that various changes and modifications may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. A thermal management package for an electronics system including a plurality of individual electronic modules secured together into a composite assembly,

at least one of said modules including a circuit board comprising a motherboard and a plurality of cell cards secured at right angles thereto and a structure of heat conductive material comprising a unitary frame enclosing a plurality of spaced webs integrally formed in said frame,

said motherboard secured to and supported by said frame and said cell cards inserted within said frame and placed in thermal contact with said webs, and

cooling means in said frame for passage of a coolant.

2. A package as in claim 1 wherein said webs have surfaces of large area, wherein each of said cell cards comprises a cell board formed of a dielectric material and components secured to only one side of said cell board, and wherein each of said cell cards is in contact with one of said web surfaces at the other side of said cell board.

3. A package as in claim 2 further including means secured to said frame and in contact with said one side of said cell board to ensure the contact between said cell board and said web.

4. A package as in claim 1 wherein said cooling means comprises a plurality of passages in said frame.

5. A package as in claim 4 wherein said cooling means further comprises fins in at least one of said passages.

6. A thermal management package for an electronics system including A a plurality of individual modules secured together into a composite assembly, at least one of said modules comprising electronic components and circuitry and a unitary frame supporting said components and circuitry, said frame including large surface area webs integrally formed in said frame, said webs having thermal contact with said electronic components and circuitry and cooling means formed in said frame adjacent to said Webs.

7. A package as in claim 6 wherein said cooling means comprises a plurality of through passage means positioned adjacent said webs.

8. A package as in claim 7 further including a plurality of frames similar to said frame such that said passage means of each of said frames are aligned to form through conduit means.

*9. A package as in claim 7 wherein said electronic components and circuitry include large surface area cell cards, said cell cards having an intimate contact with said webs.

10. A package as in claim 6 wherein said frame includes a plurality of cells bounded by said webs and further including interconnection means between said cooling means and the cells.

111. A package as in claim 10 wherein said electronic components and circuitry includes large surface area cell cards and wherein pairs of said cell cards are placed within each of the cells on both sides of said webs and in intimate contact with said webs.

'12. A package as in claim 10 further including fins in at least one of said cells having said interconnection means.

References Cited UNITED STATES PATENTS 3,209,208 9/ 1965 Francis et a1. 317'l00 3,346,773 10/1967 Lomerson 317-- ROBERT K. SCHAEFER, Primary Examiner.

M. GINSBURG, Assistant Examiner. 

